Actuated positioning device for arthroplasty and methods of use

ABSTRACT

A joint balancing insert with sensors and an actuated mechanism is disclosed. The joint balancing insert is used to balance a joint during arthroplasty surgery, as the sensors provide force, position and angular data relating to the movement of the joint, while the actuated mechanism allows for highly accurate and dynamic adjustments of the joint based on the data from the sensors. Various configurations of actuated mechanisms and sensors may be implemented in the insert to provide for manual or real time control of the insert, and customized interfaces are provided for visualized feedback of adjustments. Sensor data may also be collected and compared with expected or preferred data sets to provide adjustment recommendations and achieve better outcomes based on historical data.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/515,375 entitled “ACTUATED POSITIONING DEVICE FOR ARTHROPLASTYSURGERY AND METHODS OF USE,” filed on Oct. 15, 2014, which claims thebenefit of U.S. provisional patent application Ser. No. 61/891,397entitled “ACTUATED POSITIONING DEVICE FOR ARTHROPLASTY SURGERY ANDMETHODS OF USE,” filed on Oct. 15, 2013, U.S. provisional patentapplication Ser. No. 61/891,398 entitled “SPRING-ACTUATED POSITIONINGDEVICE FOR ARTHROPLASTY SURGERY AND METHODS OF USE,” filed on Oct. 15,2013, and U.S. provisional patent application Ser. No. 61/990,476entitled “ACTUATED POSITIONING DEVICE FOR ARTHROPLASTY SURGERY ANDMETHODS OF USE,” filed on May 8, 2014, which are hereby incorporated byreference in their entirety.

FIELD OF THE INVENTION

Various embodiments described herein relate generally to devices andmethods for balancing a joint during prosthetic arthroplasty, and to anactuated positioning and sensing device for positioning prostheticcomponents and balancing a joint during arthroplasty surgery.

BACKGROUND

Arthroplasty involves the repair of a joint by replacing one or moreportions of the joint to eliminate pain and improve movement. Forexample, loss of cartilage or friction between bone surfaces can betreated by inserting an artificial joint, which includes one or moreprostheses designed to replace bone surfaces and cartilage while alsoallowing for a range of movement similar to the original joint.

Knee arthroplasty typically involves resecting (cutting away) thediseased and damaged surfaces of the lower end of the femur (thighbone), the upper end of the tibia (shin bone), and the joint surface ofthe patella (knee cap). These surfaces are then replaced by artificialmaterials. The femoral component or prosthesis is typically made from acobalt chrome alloy and is attached to the femur with fixation devicessuch as pegs, often with the use of bone cement to bond the femoralprosthesis to the underlying bone. The tibial component typicallyconsists of two parts—a metal tray (titanium or cobalt chrome alloy) anda polyethylene insert—that are assembled together during surgery. Themetal tray is fixed to bone with screws, pegs, or a stem; while theinsert is locked into the metal tray and articulates with the femoralcomponent.

The technical challenges in knee arthroplasty are: restoration of thenatural alignment of the knee with respect to the hip and the ankle;regaining the range of motion of the knee; and inducing theartificially-implanted knee to move in a manner similar to a normalknee. These goals are accomplished by making the bone cuts at preciselocations and orientation relative to the rest of the bone, selectingthe appropriate size and shape of the prosthetic components, placing theprostheses at the appropriate location on the bones and with respect toeach other, and selecting an insert of appropriate thickness such thatthe knee joint is neither too lose or too tight.

Despite continuous improvements in the design and manufacture ofartificial joints and in surgical instruments, the actual arthroplastyrelies primarily on the skill and expertise of the surgeon performingthe procedure. Arthroplasty requires that a surgeon not only insert theartificial joint, but also “balance” the joint to ensure that themovement of the artificial joint is as similar as possible to a normalrange of motion. Balancing the joint often requires careful measurementand cutting of bone, ligaments and other tissue, as well as loadbalancing to ensure that the force applied by the bones to the joint isevenly distributed and range of motion testing to determine if theartificial joint is capable of movement in the direction and distancerequired for normal movement. The balancing process often requires thesurgeon to simply physically hold the joint and “feel” whether themovement of the joint and the forces being applied to the joint arecorrect. As a result, the process of balancing the joint is largelysubjective, as it relies upon the experience and knowledge of thesurgeon to understand whether the movement of the artificial joint is“about right.” Misalignment of any of these parameters may result inlimited range of motion of the joint, continued pain at the joint andearly failure of the artificial joint due to excess load distribution orfriction.

To aid in balancing the artificial joint during arthroplasty,measurement devices have been developed which help a surgeon measuresome parameters during the balancing of the joint. The most commonbalancing devices are mechanical in nature: the surgeon manually appliesforce on the device to distract the bones of the joints and the distancebetween the bones is visually measured. Some measurement devicesincorporate sensors which can be inserted into the artificial joint toprovide measurements about load distribution that are useful whenattempting to balance the joint. Even with these measurement devices,the surgeon is still required to manually apply an unknown or inaccurateforce to the joint in order to determine whether the joint is balanced.If the amount of applied force is inconsistent with the actual forceapplied to the joint during actual use, the joint may not moveappropriately and may wear prematurely, leading to limited movement,pain, and eventual replacement or further surgical repairs.

SUMMARY OF THE DISCLOSURE

Disclosed herein are devices and methods for balancing a joint duringsurgical procedures, such as prosthetic arthroplasty. In embodiments,the device is an insert with one or more plates, one or more sensors andat least one actuated mechanism for actuating the device against one ormore parts of the joint. The one or more plates are disposed betweenbone structures which define the joint, such as the femur and the tibiain a knee joint. The one or more sensors provide force, position andangular data about the movement of the joint, which, along with theapplied force data derived from the movement of the actuated mechanism,provide for highly accurate and dynamic adjustments of the joint. In oneembodiment, at least one actuated mechanism is a spring-actuatedmechanism. In another embodiment, at least one actuated mechanism is apneumatic-actuated mechanism. A pressurizing apparatus is used topressurize the pneumatic-actuated mechanism. Various types of actuationconfigurations, such as spring configurations and pneumaticconfigurations or a combination thereof, and sensors may be implementedin or on the insert to provide for control of the actuated mechanism andmeasurement of numerous parameters relating to the balancing of thejoint. Customized graphical user interfaces (GUIs) are provided forreal-time control and visualized feedback of adjustments. Sensor datamay also be collected and compared with expected or preferred data setsto provide adjustment recommendations and achieve better outcomes basedon historical data. Other features and advantages should become apparentfrom the following description of the preferred embodiments, taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments disclosed herein are described in detail withreference to the following figures. The drawings are provided forpurposes of illustration only and merely depict typical or exemplaryembodiments. These drawings are provided to facilitate the reader'sunderstanding and shall not be considered limiting of the breadth,scope, or applicability of the embodiments. It should be noted that forclarity and ease of illustration these drawings are not necessarily madeto scale.

FIG. 1 is a functional block diagram of a joint balancing system,according to one embodiment of the invention.

FIG. 2 is an illustration of an embodiment of the insert of FIG. 1disposed in a knee joint.

FIG. 3 is a perspective view illustration of an embodiment of the insertof FIG. 1 with displacement sensors.

FIG. 4 is an illustration of a perspective view of an embodiment of theinsert of FIG. 1 with a pneumatic actuator.

FIG. 5 is an illustration of an exploded view of the insert of FIG. 4.

FIG. 6 is an illustration of a perspective view of the pneumaticactuator of FIGS. 4 and 5.

FIG. 7 is a top view of a bellows 182 of FIG. 6.

FIG. 8 is an illustration of a perspective view of the electronics boardof FIGS. 4 and 5.

FIG. 9 is an exploded view illustration of an embodiment of the insertof FIG. 1 with a plurality of spring actuators.

FIG. 10 is an alternate exploded view illustration of the insert of FIG.9 without the actuators.

FIG. 11 is a perspective view illustration of an embodiment of theinsert of FIG. 1 with a unicompartmental configuration.

FIG. 12 is an illustration of a perspective view of an embodiment of thecontroller assembly of FIG. 1 connected to an insert.

FIG. 13 is an illustration of a perspective view of the controller ofthe controller assembly of FIG. 12.

FIG. 14 is an illustration of an exploded view of the controller of FIG.13.

FIGS. 15 and 16 illustrate an embodiment of a cutting guide assemblyconnected to the insert that is used to guide cutting bone and tissueduring balancing of the joint.

The various embodiments mentioned above are described in further detailwith reference to the aforementioned figured and the following detaileddescription of exemplary embodiments.

DETAILED DESCRIPTION

Disclosed herein are systems, devices, and methods for balancing a jointduring surgical procedures on joints, such as prosthetic arthroplasty.FIG. 1 is a functional block diagram of a joint balancing system 50,according to one embodiment of the invention. Joint balancing system 50may include a trial insert (“insert”) 100, a controller assembly 200,and a display system 300. The joint balancing system 50 includes aninsert 100 with one or more plates, one or more sensors and at least oneactuator/actuated mechanism for actuating the device against one or moreparts of the joint as illustrated in FIGS. 2-11. The actuated mechanismmay be fluid powered, such as by air, electromechanical,electromagnetic, mechanical, piezoelectric, or a combination thereof.Other actuated mechanisms may also be used. The one or more plates aredisposed between bone structures which define the joint, such as thefemur and the tibia in a knee joint. The one or more sensors may provideforce, position and angular data about the movement of the joint, which,along with the applied force data from the actuation mechanism, providefor highly accurate and dynamic adjustments of the joint. Variousconfigurations of the actuators and sensors may be implemented in or onthe insert 100 to provide for control of the insert 100 and measurementof numerous parameters relating to the balancing of the joint. Theaddition of an actuated mechanism to the inserts provides numerousbenefits to the process of balancing a joint during surgical procedures,such as arthroplasty. The surgeon is able to apply a known andcontrolled amount of force to the joint and correlate the measured load,movement and angular data with the applied force to more preciselydetermine if adjustments should be made. The actuated mechanism may alsobe capable of dynamic actuation from a variety of different actuationpoints on the insert, providing the ability to apply different loadamounts, different amounts of movement and different angles of movementto more accurately simulate the movement of the joint and measure theresults. The load can be measured across any range of motion to providesignificant improvements in load balancing.

The insert 100 may include an electronics board 140. The electronicsboard 140 may include a board module 141 and a board communicationmodule 143. The board module 141 may be configured to obtain the datafrom the sensors and send the data to the controller assembly 200 viathe board communication module 143. The board module 141 may also beconfigured to relay a signal from the controller assembly 200 to theactuators. The board module 141 may also be configured with a safetyoverride to control the actuator force or the magnitude of distractionor displacement. The board module 141 may further be configured tocommunicate a signal when the insert 100 is unbalanced and communicateanother signal when the insert is balanced. The signal may cause analert, such as an auditory alert or a visual alert provided byelectronic hardware attached to the electronics board 140 and/or fromthe display system. The auditory alert may be provided by a soundsource, such as a speaker or a piezoelectric sound generator. The visualalert may be provided by a light source, such as a light emitting diode.The board module 141 may yet further be configured to provide guidancefor alignment during surgery to surgical instruments, such as drills andsaws. The communications module 143 may be configured to send/receiveelectronic signals to/from the controller assembly over a wired orwireless connection. In some embodiments, the communications module 143is configured to communicate with other surgical instruments such asdrills and saws.

The controller assembly 200 may be used to manually or remotely controlthe actuators within the insert 100. In some embodiments, the controllerassembly 200 physically or mechanically controls the actuators which mayallow for manual manipulation of the movement of the actuators by asurgeon or medical technician. In other embodiments, the controllerassembly 200 electronically controls the actuators which can bemonitored and programmed as a computing device with a processor andmemory.

Controller assembly 200 may include a controller 240. Controller 240 mayinclude a controller communication module 259. The controllercommunication module 259 is configured to send/receive signals from theinsert 100 and from the display system 300 over a wired and/or awireless connection. In some embodiments, the controller communicationmodule 259 is configured to communicate with other surgical instruments,such as drills and saws. The controller communication module 259 mayrelay the guidance provided by the board module 141 to the surgicalinstruments.

Controller assembly 200 may be manipulated through one or more inputdevices, such as a mouse, a keyboard, capacitive buttons, or aninteractive display. The interactive display may be part of the displaysystem 300 and may display the controls for each actuator along with therelevant values and other measured parameters for easy comparison duringjoint balancing. A single controller 240 may be configured to apply thesame pressure to all of the actuators. This may simplify the design andensure that an equal force/pressure is applied at each actuator.

Display system 300 may be a computing device with a processor andmemory, such as a computer, tablet, smartphone, or other electronicdevice that may be used to display the GUI. Display system 300 mayinclude a display communication module 310, a display module 320, and adisplay 330, such as a monitor. Display communication module 310 isconfigured to send/receive wired or wireless communications to/from thecontroller assembly 200.

Display module 320 may provide customized graphical user interfaces(GUIs) for viewing on display 330. The GUIs may display relevant datafor real-time control and visualized feedback of adjustments throughvisual alignment guides that indicate when all of the measuredparameters are within preferred ranges. The GUIs may also present thevalues for the parameters measured by the various sensors.

Sensor data may also be collected and compared with expected orpreferred data sets to provide adjustment recommendations and achievebetter outcomes based on historical data. A GUI may provide visual oraudio indications as to whether the joint is balanced by comparing themeasured parameters with known accepted ranges of the values. Inembodiments, the GUI may provide the force applied to the top plate 110and the bottom plate 150. The force may be determined using the heightand pressure measurements provided by the sensors. The force may bedetermined by the display system 300, such as by the display module 320,or by another system/module.

Joint balancing system may also include a data store 90. The data store90 may be a separate system connected to either the display system 300or the controller assembly 200, or may be located within either thedisplay system 300 or the controller assembly 200. In embodiments, thedata in the data store 90 may be uploaded to a central server foranalysis.

In one embodiment, a visual alignment guide may be presented whichgraphically illustrates the alignment of the two plates and the movementof the actuators within the joint in real-time. The visual alignmentguide may provide guide lines or circular targets that will help thesurgeon achieve a desired alignment. The alignment guide may alsoprovide color-coded visual graphics to indicate whether an alignment isgood (green) or bad (red).

In some embodiments, the GUI displays one or more diagrams related tothe positioning of the insert 100. The diagrams may display the relativedisplacement between the top and bottom plates in one or more of thesensor locations. The GUI may also display the tilt between the top andbottom plates. The GUI may include multiple graphs. One graph maydisplay the history of the tilt in the mediolateral (side to side)direction. Another graph may display the tilt in the anteroposteriordirection. The GUI may also display the knee flexion angle, pressure,force, and battery voltage. The GUI may also provide buttons to save thedata or to generate a screen capture for future reference. This data andinformation may be archived in the data store 90. A third graph maydisplay the history of the distance between the top and bottom plates.The GUI may also display previously recorded data against which the realtime data can be compared.

In some embodiments, the GUI displays three diagrams. One diagramdisplays the data collected while the knee is at 0 flexion, anotherdiagram displays the data collected while the knee is at 90 degreesflexion, and the third diagram displays the data in real time.

In some embodiments, the GUI can be used prior to surgery to set up acustom or patient-specific balance that is unique to the patent and/orthe insert 100. The GUI can also contain a list of instructions as towhere the problem is within the joint and can provide a recommendationto the surgeon on how to correct the problem. The GUI can also displayinformation from other devices or instruments, such as computernavigation systems, surgical robots, instruments, such as drills andsaws, tourniquet sensors, etc.

FIG. 2 is an illustration of an embodiment of the insert 100 of FIG. 1disposed in a knee joint. In the embodiment illustrated, the insert 100includes a top plate 110 and a bottom plate 150 separated by actuators180 positioned at various points on the interior surfaces of the topplate 110 and bottom plate 150. The top plate 110 is disposed against afemur 8, while the bottom plate 150 is disposed against a tibia 10. Theinsert 100 is additionally configured with one or more sensors (shown inFIG. 3) disposed along the top plate 110 and/or the bottom plates 150.The sensors are configured to measure and determine various parametersrelated to the balancing of the joint, as described herein.

The insert 100 may be designed as a temporary insert that is positionedinto the joint only during a joint balancing procedure, such that it isreplaced by a permanent insert of similar shape and size once the jointbalancing is complete. In another embodiment, the insert 100 may bepermanent, such that it will remain in position between the adjacentbones once the joint has been balanced.

The insert 100 may be a standalone device before insertion into thejoint. The top plate 110 and bottom plate 150 may vary in shape and sizeand be aligned in parallel planes. The general shape of the top plate110 and corresponding bottom plate 150 (is designed to fit within theknee joint and provide a large surface area to interface with, such asby contact, the bony surfaces of the adjacent femur 8 and tibia 10. Inthe embodiment illustrated, insert 100 includes four total actuators 180(three visible) disposed between the top plate 110 and the bottom plate150. The actuators 180 may be evenly spaced and positioned withindifferent quadrants of the insert 100 to provide for actuation fromdifferent points within the insert that will allow for dynamic loadbalancing at each actuator and different angles of actuation of theinsert 100. For example, if two adjacent actuators 180 are actuated, theinsert may be disposed at an angle which slopes from one side of theinsert 100 to the other. The number of actuators 180 may vary and may beas few as one. The actuators 180 may be placed in other configurations,such as triangular, circular, or irregular placements. The actuators mayalso be tilted or angled to generate shear or rotational forces(torque).

A method of balancing a joint using the insert 100 in accordance withone embodiment of the invention will now be described. The balance ofthe joint may be measured at several stages of the surgical procedure.For example: measurements may be taken before making any bone cuts, orafter making the tibial bone cut against the uncut femoral surface, orafter making the femoral cut against the cut femoral surfaces or againsta trial femoral prosthesis, or with trial femoral or tibial prosthesesin place, or with the final femoral and tibial prostheses in place.During a first step, the insert is positioned in a gap or opening of ajoint between two opposing bone structures, such as an opening between afemur 8 and a tibia 10 in a knee joint. In some embodiments,insertion/extraction tools are used to insert the insert 100 into theopening. Next, one or more of the actuators 180 is activated to apply aload to the bone structures of the femur 8 and tibia 10. The sensorsmeasure one or more parameters relating to the joint, such as themovement, pressure, angle, position, range of motion, gap, load appliedby each actuator, etc. The measurements may provide an indication as towhether the joint is balanced—i.e. whether pressure is being evenlyapplied to the insert by the opposing bone structures, whether the jointis able to move within a desired range of motion, the magnitude of thegap between the surfaces of the femur 8 and tibia 10 and the change ingap when the knee is flexed or extended, whether the ligamentssurrounding the joint are under too much tension, etc. The measurementsmay also indicate that the bone cuts are not optimum, for example, thetibia 10 may have been cut in too much varus or valgus, the femur 8 mayhave been cut in too much varus or valgus, or in external or internalrotation, or the distal cut of the femur may have been made too deepresulting in a mismatch of the gap between the surfaces of the femur andtibia at different flexion angles. If the measurements and analysis ofthe measurements indicates that the joint is not properly balanced orthe bone cuts are not appropriate, the surgeon will make one or moreadjustments to some portion of the joint to improve the balance of thejoint. The adjustments may include: re-cutting the bones, releasing ortightening ligaments, adjusting the placement or rotation of theprosthetics or the insert 100; cutting away portions of the bones,ligaments or cartilage; or increasing or decreasing the height of theinsert 100 to better fit the gap in the joint. The joint may be testedagain by actuating one or more of the actuators and measuring theparameters to determine if improvements have been made. This process maybe repeated till the surgeon is satisfied with the measurements. Inembodiments including a fluid powered actuator, measuring thedistraction while changing the pressure of the fluid powered actuatormay be used to characterize the biomechanical properties of the softtissues and aid in selecting the optimal balance.

At the point where the measurements fall within certain acceptableranges, the joint is considered to be balanced. If the insert 100 isdesigned to function as a permanent prosthetic, it is left in place inthe joint opening. If the insert 100 is configured only as a measurementand testing tool, it is removed and then replaced with a permanentprosthesis of identical dimensions. In some embodiments, the datacollected by the sensor(s) are used to generate a custom implant ondemand.

Further details of the properties and function of the insert 100 will bedescribed below with regard to the actuators, sensors, shape andconfiguration of the device, controllers and user interface andadditional tools for joint balancing.

Sensors

Sensors disposed on or within the insert 100 can be configured tomeasure and be used to determine numerous different parameters relatedto the balancing of the joint. For example, the sensors can beconfigured to measure and be used to determine the force, or load, beingapplied by the actuators and the resulting pressure received on varioussections of the top or bottom plates by the adjacent bone. Examples ofthese sensors are load cells, strain gages, pressure sensors, etc. Forspring actuators, the spring force may be calculated indirectly, forexample using the known spring stiffness and the measured spring lengthusing displacement sensors. Sensors can also be configured to monitordistance of movement, either total movement between the top and bottomplates or movement of each individual actuator. Examples of thesesensors are magnetic sensors, optoelectric sensors, and monitoring thestroke of the actuator mechanism (e.g. screw driven actuators). Sensorsmay also measure angles of motion, and even angular positions throughthe use of accelerometers, magnetometer, and gyroscopes.

The inserts 100 may incorporate a plurality of different sensors inorder to measure different types of parameters or to measure the sametypes of parameters at different places on the insert 100. The sensorscommunicate via a wired or wireless connection, and may be powered by anexternal power source or an internal power source within each sensor ora power source located within the insert 100.

FIG. 3 is a perspective view illustration of an embodiment of the insert100 of FIG. 1 with sensors 102. The actuators 180 are not shown forclarity. Sensors 102 may be used to determine the relationship betweenthe top plate 110 and the bottom plate 150, such as the spatialrelationship, including the distance and angle between the top plate 110and bottom plate 150, and the pressure between the top plate 110 and thebottom plate 150. In the embodiment illustrated, sensors 102 aredisplacement sensors with corresponding magnets 104. The sensors 102 andmagnets 104 may be located on opposite interior surfaces of the topplate 110 and the bottom plate 150. Insert 100 may include any numberand configuration of sensors 102 and magnets 104. In the embodimentillustrated, the insert 100 has four sensors 102 on an interior surfaceof the bottom plate 150 and four corresponding magnets 104 configured onan interior surface of the top plate 110 for holding the two platestogether. The sensors 118 measure displacement between the top plate 110and bottom plate 150 at multiple locations and calculate tilt in twodirections. The sensors 102 may be Hall Effect sensors. The sensors 102and magnets 104 may be aligned between the top plate 110 and the bottomplate 150.

In some embodiments, a single sensor 102 is positioned in a center areaof the insert 100, such that the top plate 110 and bottom plate 150pivot around the sensor 102 and the corresponding magnet 104. The singlesensor 102 is therefore able to measure displacement between the topplate 110 and the bottom plate 150, as well as rotational movement inthree directions. In one embodiment, the single sensor 102 is a threedimensional magnetometer.

In some embodiments, the sensor 102 is a pressure sensor. In theseembodiments, the sensor 102 may cover a substantial portion of a surfaceof the top plate 110 or bottom plate 150 and may adjoin that surface. Inthese embodiments, the pressure sensors may be configured such that apressure map can be determined and provided by the GUI including therelative position of femoral condyles during the balancing of a knee. Inone embodiment, the sensor is positioned above a substantial portion ofan interior surface of the bottom plate 150. In another embodiment, thesensor 102 is positioned on an exterior surface of the bottom plate 150.In yet another embodiment, the sensor 102 is positioned on an interiorsurface of the top plate 110. In a further embodiment, the sensor 102 ispositioned on the articular exterior surface of the top plate 110. Thesensor 102 is capable of measuring pressure distribution over the entiresurface area of the adjoining surface and may be configured to measurecontact pressure between the femur 8 and tibia 10.

Additionally, one or more of the sensors 102 may be angle measurementsensors (including accelerometers, magnetometers and gyroscopes) thatare configured to measure the angle of the insert relative to the leg,thigh, or any other part of the body, as well as relative to the ground.This information can be used to determine whether there is an imbalancein the joint and to assess if the imbalance is due to ligament imbalanceor improper bone cuts.

Pneumatic-Actuated Mechanisms

In some embodiments, the insert 100 may be actuated by fluid power, suchas by pneumatics or hydraulics. Fluids such as air, saline, or moreviscous fluids, such as gels, may be used to as the actuating fluid.FIGS. 4-7 illustrate an embodiment of the insert 100, where the insert100 is a pneumatic insert. FIG. 4 is an illustration of a perspectiveview of an embodiment of the insert of FIG. 1 with a pneumatic actuator180.

In the embodiment illustrated, top plate 110 includes a plate portion120 and an articular portion 130. The articular portion 130 attaches toplate portion 120 and is configured to interface with, such as by director indirect contact, the natural or artificial femur. The top plate 110or bottom plate 150 may include one or more grooves 138. The grooves maybe oval shaped to match the natural shape of the condyles of theadjacent bone. In the embodiment illustrated, grooves 138 are located onthe outer surface of the top plate 110 with a groove 138 on each side ofthe top plate 110 which would receive corresponding condyles 114 (seeFIG. 2) of the femur 8.

The grooves 138 may include an articular contact surface 139 thatarticulates with the articular surface of the natural or artificialfemur. In the embodiment illustrated, the grooves 138 and articularcontact surface 139 are located on an outer surface of the articularportion 130, located opposite both the top portion 120 and the bottomplate 150. The articular portion 130, including the grooves 138 and thearticular contact surfaces 139, can be shaped to accommodate any femoralarticular size or shape.

FIG. 5 is an illustration of an exploded view of the insert 100 of FIG.4. The actuator 180 is located between the top plate 110 and the bottomplate 150. The top plate 110 and the bottom plate 150 may be combined toor may individually match the natural shape of the tibial bone or matchthe shape of an implant, such as a tibial tray. A pneumatic actuator 180may be formed of one or more bellows. The actuator may include multipleconfigurations of bellows, such as first bellows 181 and second bellows182. In the embodiment illustrated, the actuator 180 includes fourlayers of bellows with one first bellows 181 and three second bellows182. In embodiments, the first bellows 181 and the second bellows 182are stacked between the top plate 110 and the bottom plate 150. Theactuator 180 is connected and fluidly coupled to a fluid supply line 70.The fluid supply line 70 allows the fluid, such as air, to be added orremoved from the one or more bellows to position the top plate 110relative to the bottom plate 150.

Plate portion 120 may include a plate body 121, a board receivingfeature 124, a connection feature 128, and a connection hole 129. Platebody 121 may include a plate body connection end 122, a plate bodyinsertion end 123, a plate body first side 124, and a plate body secondside 125. Plate body connection end 122 may generally have a convexshape. The curvature of the convex shape may be similar to the curvatureof the flatter portion of an ellipse. Plate body insertion end 123 isopposite plate body connection end 122. Plate body insertion end 123 mayinclude a concave portion and may generally have the shape of a portionof a Cassini oval that is between an oval and a lemniscate. Plate bodyfirst side 124 and plate body second side 125 may be symmetrical and mayeach have a circular shape. Plate body connection end 122, plate bodyinsertion end 123, plate body first side 124, and plate body second side125 may form the perimeter of plate portion 120.

Board receiving feature 126 may protrude from plate body 121 towardsarticular portion 130 and away from bottom plate 150. Board receivingfeature 126 may generally include a T-shape. Board receiving feature 126may also include a cavity for receiving electronics board 140. Boardreceiving feature 126 may further include one or more electronicsreceiving features 127. The electronics receiving features 127 may be aprotrusion or a recess configured to receive electronic hardware 142coupled to electronics board 140.

Connection feature 128 may extend from plate portion 120 at plate bodyconnection end 122 generally towards bottom plate 150. Connectionfeature 128 may extend in the opposite direction relative to boardreceiving feature 124. Connection hole 129 may extend through connectionfeature 128 to provide access to electronics board 140.

Articular portion 130 may include an articular portion body 131, arecess 137, and a connection end bevel 136 along with the grooves 138and the articular surfaces 138. Articular portion body 131 may generallyinclude the same shape about its perimeter as plate body 121. Articularportion body 131 may include an articular portion body connection end132, an articular portion body insertion end 133, an articular portionbody first side 134, and an articular portion body second side 135.Articular portion body connection end 132 may generally have a convexshape. The curvature of the convex shape may be similar to the curvatureof the flatter portion of an ellipse. Articular portion body insertionend 133 is opposite articular portion body connection end 132. Articularportion body insertion end 133 may include a concave portion and maygenerally have the shape of a portion of a Cassini oval that is betweenan oval and a lemniscate. Articular portion body first side 134 andarticular portion body second side 135 may be symmetrical and may eachhave a circular shape. Articular portion body connection end 132,articular portion body insertion end 133, articular portion body firstside 134, and articular portion body second side 135 may form theperimeter of articular portion 130.

Recess 137 may be located opposite grooves 138 and articular surfaces139. Recess 137 may include a T-shape and may be configured to receiveboard receiving feature 126. Connection end bevel 136 may be located atconnection end 132 and may be centered in connection end 132 between togrooves 138.

The insert 100 may include attachment mechanisms 112. Attachmentmechanisms 112 may be fasteners, such as detent posts. The articularportion 130 may be attached to the top portion 120 using the attachmentmechanisms 112. Screws 113 may extend through and up from boardreceiving feature 126. Attachment mechanisms 112 may be configured tocouple to screws 113 to hold plate portion 120 to articular portion 130.

The bottom plate 150 may include a bottom plate body 151, one or moremagnet recesses 156, a connector recess 157, and restraining holes 158.The bottom plate body 151 may generally include the same shape about itsperimeter as plate portion body 121 and articular body portion 131.

Bottom plate body 151 may include bottom plate body connection end 152,a bottom plate body insertion end 153, a bottom plate body first side134, and a bottom plate body second side 155. Bottom plate bodyconnection end 152 may generally have a convex shape. The curvature ofthe convex shape may be similar to the curvature of the flatter portionof an ellipse. Bottom plate body insertion end 153 is opposite bottomplate body connection end 152. Bottom plate body insertion end 153 mayinclude a concave portion and may generally have the shape of a portionof a Cassini oval that is between an oval and a lemniscate. Bottom platebody first side 154 and bottom plate body second side 155 may besymmetrical and may each have a circular shape. Bottom plate bodyconnection end 152, bottom plate body insertion end 153, bottom platebody first side 154, and bottom plate body second side 155 may form theperimeter of plate portion 120.

Each magnet recess 156 may extend into bottom plate body 151 from aninterior surface of bottom plate body 151 and may be configured to holdone or more magnet 104. In the embodiment illustrated, insert 100includes one magnet in each magnet recess 156. Each magnet recess 156may be adjacent actuator 180. The embodiment illustrated includes threemagnet recesses 156 arranged in a triangular pattern. In otherembodiments, different numbers of magnetic recesses 156 and magnets 104are used and arranged in different patterns. Each magnet recess 156 andthe magnet 104 therein may be aligned with a sensor 102.

Connector recess 157 may extend into bottom plate body 151 from bottomplate body connection end 152. In the embodiment illustrated, connectorrecess 157 is a cuboid shaped recess. Connector recess 157 is configuredso that bottom plate 150 does not interfere with connector feature 128when actuator 180 is in its narrowest configuration, such as when thebellows 182 are empty.

Restraining holes 158 may be used to secure bottom plate 150 to topplate 110. The insert 100 may include a restraining device 115. Therestraining device 115 is configured to hold the top plate 110 and thebottom plate 150 together. The restraining device 115 is also configuredto prevent the top plate 110 and the bottom plate 150 from separatingbeyond a desired distance and is configured to allow the actuator 180 toexpand up to a predetermined amount. In the embodiment illustrated, thepredetermined amount of expansion is 6 millimeters, which may allow theinsert 100 to expand from eight millimeters to fourteen millimeters. Inthe embodiment illustrated, the restraining device 115 is made ofmedical suture material. In other embodiments, the restraining device115 is integral to each chamber of the pneumatic actuator 180. In otherembodiments, the restraining device 115 is a skirt around the perimeterextending between the top plate 110 and the bottom plate 150. Someembodiments may be configured to expand beyond fourteen millimeters.Other embodiments are configured shims are added to the bottom plate 150to increase the distraction. In yet other embodiments, an articularportion 130 with an increased thickness is attached to the top plate 110to further expand the height of the insert 100 beyond fourteenmillimeters.

In the embodiment illustrated, the insert 100 includes two restrainingdevices 115, one on each side of the insert 100. The restraining device115 may contact the outer surface of the bottom plate 150, pass throughthe restraining holes 152 and be affixed to the top plate 110. In theembodiment illustrated, each restraining device 115 is affixed to thetop portion 120 with retaining fasteners 124, such as screws.

The insert 100 may also include an electronics board 140. Theelectronics board 140 may be housed within the top plate 110 or thebottom plate 150. In the embodiment illustrated, the electronics board140 is located within board receiving feature 126 and is adjacentactuator 180. An electronics connector 60 may be electronically coupledto the electronics board 140 and may extend from the electronics board140, through connector hole 129, and to the controller assembly 200. Theelectronics connector 60 may be an electric wire with an outer casing.Electronic hardware 142 may be coupled to and adjacent the electronicsboard 140. The electronic hardware 142 may include sensors, soundsources, such as speakers and piezoelectric sound generators, and lightsources, such as light emitting diodes.

FIG. 6 is an illustration of a perspective view of the pneumaticactuator 180 of FIGS. 4 and 5. FIG. 7 is a top view of the first bellows181 of FIGS. 5 and 6. Referring to FIGS. 6 and 7, each bellows is madeof an inflatable material that includes one or more pneumaticcompartments 187 surrounded by a compartment boundary 188. The bellowsand the various compartments 187 are manifolded together. In theembodiment illustrated, the bellows have manifolds between compartments187 of adjacent bellows as described herein. In other embodiments, amanifold can be used to plumb each bellows separately. In otherembodiments, each bellows is plumbed to a separate fluid source andactuated separately. The pneumatic compartments are configured toinflate such that the pneumatic compartments expand and distribute thepneumatic force over different regions of the top plate 110 and bottomplate 150. The shape, size, and number of layers of the bellows 182within the actuator 180 may be selected based on the desired force at agiven pressure. In embodiments, the nominal force is 20 lbf. In someembodiments, the force should not vary by more than 15%. In someembodiments, the force should not vary by more than 3 lbf.

The shape of the bellows 182 may also be configured to maximize thetransmission of forces as well as the magnitude of distraction. Changingthe shape of the bellows 182 may change the surface area which maychange the magnitude of the force (for the same pressure). Changing theshape of the bellows 182 can also affect the location of the center ofapplication of the force.

In the embodiment illustrated, the first bellows 181 and the secondbellows 182 have the same general dog bone shape. The first bellows 181has four compartments 187 with each compartment 187 in one quadrant ofthe first bellows 181. Each compartment 187 is a quarter of the dog boneshape. In the first bellows 181 the four compartments 187 are in directfluid communication. The compartment boundary 188 for each compartmentis open to the other compartments 187 along the neck of the dog boneshape. The first bellows 181 may include a fluid communication hole 184through the top of each compartment 187, on the bottom of eachcompartment 187, or through both.

The first bellows 181 also has a fluid connection tab 189 and a fluidsupply connector 183. The fluid connection tab 189 may extend out fromthe neck of the dog bone shape and be in fluid communication with thefluid supply connector 183. The fluid supply connector 183 is configuredto fluidly connect the first bellows 181 to the fluid supply line 70.

The second bellows 182 has four compartments 187 with each compartment187 in one quadrant of the second bellows 182. Each compartment 187 is aquarter of the dog bone shape. In the second bellows 182 the fourcompartments 187 are not in direct fluid communication. The compartmentboundary 188 for each compartment completely encloses the compartmentoff from the other compartments 187. The second bellows 182 may includea fluid communication hole 184 through the top of each compartment 187,on the bottom of each compartment 187, or through both.

The actuator 180 may include multiple annular seals 186 and multipleseals 185. In the embodiment illustrated, annular seals 186 are adhesiverings and seals 185 are adhesive disks. In other embodiment, annularseals 186 and seals 185 are formed by bonding the bellows to theadjacent structure, such as an adjacent bellows, a top plate 110, or abottom plate 150. In some embodiments, the annular seals 186 and seals185 are formed using RF welding. An annular seal 186 may be locatedbetween adjacent compartments 187 of adjacent bellows, such as the firstbellows 181 and a second bellows 182 or two adjacent bellows 182. Theannular seal 186 seals the adjacent compartments 187 around the adjacentfluid communication holes 184 so that the adjacent compartments 187 aremanifolded together in fluid communication. In embodiments, the annularseals 186 and manifold formed by thereby can withstand a vacuum. Theseals 185 are located at the outer surface of a compartment 187 that isnot adjacent to another compartment 187. The seals 185 may be configuredto seal a fluid communication hole 184 and may attach the first bellows181 or the second bellows 182 to either the top plate 110 or the bottomplate 150.

FIG. 8 is an illustration of a perspective view of the electronics boardof FIGS. 4 and 5. The electronics board 140 may include a board surface731 that faces the bottom plate 150 with the actuator 180 there between(as shown in FIGS. 5 and 6). One or more sensors 102 may be connected tothe electronics board 140. The location and number of sensors 102 maycorrespond to the number and placement of the one or more magnets 104located at the bottom plate 150 (shown in FIG. 7B). The sensors 102 maydetect the distance from the magnets 104, which may allow the distanceand the angle between the top plate 110 and the bottom plate 150 to bedetermined.

Spring-Actuated Mechanisms

In some embodiments, the insert 100 is configured with one or moremechanical actuators 180, such as constant or variable force springs,which apply a load to the plates and the adjoining bone structures ofthe joint. The number and type of actuators 180 may vary depending onnumerous factors, including the intended function of the device and theamount of control needed over the actuation process.

FIG. 9 is an exploded view illustration of an embodiment of the insertof FIG. 1 with a plurality of spring actuators. Referring to FIG. 9, theactuators 180 are springs. The actuators 180 are not permanentlyattached with the top plate 110 and bottom plate 150 and can thereforebe easily removed in order to exchange them with different actuatorsthat have a different stiffness. In addition, the unattached actuators180 also allow for the exchange of the top plate 110 and/or bottom plate150 with plates of different size, shape and thickness in order to bestmatch the needed dimensions of the area where the insert 100 is beingpositioned. The unattached actuators 180 may then be secured within theinsert 100 by providing top actuator recesses 111 in top plate 110 andbottom actuator recesses 161 in bottom plate 150. The top plate 110 andbottom plate 150 may also be connected with each other by a flexible orelastic tether that holds the entire insert assembly together.

Alternatively, the actuators 180 may be attached (either permanently orremovably) with the top plate 110 or bottom plate 150 (or both) by oneor more attachment mechanisms. In one example, the ends of the actuators180 may be bonded to the top plate 110 and the bottom plate 150 withvarious glues such as cyanoacrylate or potted in plate with epoxy,polyurethane, etc. The actuators 180 could also be manufactured withcustomized ends which snap into a corresponding retaining mechanism onthe respective top plate 110 and bottom plate 150 and lock the ends ofthe actuators 180 into place. The actuators 180 could also bemanufactured and formed within one or both of the top plate 110 andbottom plate 150.

The shape and dimensions of the spring-actuated mechanism may also varyconsiderably, but in the embodiments described and illustrated herein,the actuators 180 are springs which are cylindrically-shaped with adiameter of approximately 4-8 millimeters (mm) and an expandable heightof approximately 6-10 mm. The actuators 180 may be configured to apply aforce in the range of 1-50 pounds per actuator, have a force accuracy ofapproximately 1 percent and a displacement accuracy of approximately 0.2mm. When a plurality of actuators 180 are used, each actuator 180 may beindependently controlled and expanded or contracted in order to obtainan angled, or tilted top plate 110 or bottom plate 150, as has beenpreviously described. The number of actuators 180 used may vary betweenone to four or more, and may depend on the size of the actuator 180 andsurface areas of the top plate 110 and the bottom plate 150 on whichthey are disposed. The actuators 180 may have varying stroke lengths,shapes, dimensions and force capacities.

In one embodiment, actuators 180 are helical or coil springs thatgenerate force when compressed. In another embodiment, actuators 180 areconical or volute springs, in which the coils slide over each other,thus permitting greater travel for the same resting length of thespring. In yet another embodiment, actuators 180 are cantilever springsthat bend when compressed. The springs could be made of common materialssuch as metals (steel, titanium, aluminum), polymers, or rubbers. In theembodiment illustrated in FIG. 9, 4 coil springs are located between atop plate 110 and bottom plate 150. The bottom plate 150 may contain theforce, displacement, and angle measurement sensors, a microprocessorpowered by a battery, and a radio for wireless communication.

Different configurations of actuators 180 provide advantages anddisadvantages. The choice of a particular configuration of actuators 180may therefore depend on the specific intended use and desired featuresfor the actuation and measurement, which could vary from one surgeon toanother. The use of a mechanical spring as an actuator would allow forthe insert to be an entirely wireless device. Wireless sensors coupledwith constant force springs provide an insert which would not requireany physical connections, and as such could be easily removed andreplaced during the balancing process. In addition, a spring-actuateddevice could be permanently implanted into the joint, whereas otherinserts would need to be removed and then replaced with anidentically-shaped permanent prosthesis. In a further embodiment, theactuators may be locked into a final position and then disconnected fromthe external controller and power source.

FIG. 10 is an alternate exploded view illustration of the insert 100 ofFIG. 9 without the actuators. In the embodiment illustrated, bottomplate 150 includes an electronics recess 162 extending from the outersurface of the bottom plate body 151, opposite the bottom actuatorrecesses 161. The electronics recess 162 may house the electronics board140 and other electronics, such as any sensors, microprocessors, powermodules or radios which communicate the sensed data to. The insert 100may include a bottom plate cover 163 that connects to the bottom platebody 151 and covers the electronics recess 162.

Materials, Shapes and Configurations

The insert 100 may be made from any combination of biocompatible ormedical-grade polymers or metal alloys, as known to one of skill in theart. The biocompatible material may be rated for limited contact. Thematerials would be required to meet structural and mechanicalspecifications needed to sustain the pressures, temperatures, fluids andfrictions with other components of the insert and any adjoining bonesurfaces, cartilage, ligaments and other tissues. The material of thetop plate 110 and in particular of the articular contacting surface 139should be a material that will not damage the articular surface of thefemoral bone or component. The insert 100 should also be made frommaterials which can be sterilized in order to minimize the risk ofinfection during surgery. The material requirements will also apply tothe actuators and in some aspects to the sensors, particularly withregard to the sterilization and durability requirements. In embodiments,the insert 100 may include radiopaque markers or material for use influoroscopic x-ray verification.

The size of the insert 100 may vary depending on the patient or the typeof joint. The insert could conceivably be manufactured in severaldifferent sizes for different sized joints, such as a small, medium andlarge option. In one embodiment, a medium-sized insert would beapproximately 70 millimeters (mm) by 45 mm and have an adjustable heightof 8-14 mm. The height of the insert may need to be adjusted separatelyfrom the actuation mechanism in order to initially fit within the spaceof the joint between opposing bone structures. This may be accomplishedusing shims. In some embodiments, shims include a height from 1-6 mm andmay be provided in 1 mm increments. In embodiments, the articularportion 130 may be switched out for one with a different height for theinitial fit of the insert 100 within the space of the joint. Theactuator 180 could then provide additional movement and spacing of atleast a maximum height change. In one embodiment, the maximum heightchange of the insert is of 4-8 mm. In another embodiment, the maximumheight change is 5-7 millimeters. In yet another embodiment, the maximumheight change is at least 6 mm. The other dimensions of the device mayalso be adjustable in order to better fit a desired shape and size ofthe joint and the adjoining bones, ligaments or cartilage. The insert100 may also be configured to be stable in shear between the top plate110 and the bottom plate 150 throughout the range of motion of the knee.In some embodiments, the stiffness of the bellows under inflation may beconfigured to resist shear. In embodiments, the insert can resist a sideload of 5 lbf. In some embodiments, the range of dynamic knee flexionangle measurement of the insert 100 may be from 10 degrees ofhyperextension to 140 degrees of flexion.

The shape of the insert may also vary depending on the intended use ofthe device. The insert 100 may have a tricompartmental, bicompartmental,or a unicompartmental design. The embodiments illustrated in FIGS. 2 to10 have a tricompartmental design. FIG. 11 is a perspective viewillustration of an embodiment of the insert of FIG. 1 with aunicompartmental configuration. The insert 100 with a unicompartmentaldesign may be essentially half of the tricompartmental design bisecteddown a longitudinal middle of the device. The insert 100 with aunicompartmental design still includes a top plate 110 and a bottomplate 150 separated by one or more actuators. An insert 100 with aunicompartmental design may be advantageous for various types ofsurgical procedures, such as arthroplasty, in particular a partial kneereplacement where only one half of the knee joint is replaced. A partialknee replacement arthroplasty preserves some of the ligaments in theknee, and the insert 100 can be placed on only one half of the joint toallow for balancing of the joint with actuation that similarly avoidsthe need to remove additional ligaments in the knee. The number ofactuators in a partial knee replacement may vary according to userpreference or the specifications of the joint balancing process whenonly part of the knee joint is being replaced.

Multiple inserts 100 with a unicompartmental design may also be utilizedin a full knee replacement where the central cruciate ligaments are tobe preserved by sliding each insert 100 from lateral sides of the kneejoint.

The top plate 110 and the bottom plate 150 may be modular to allow foreasy placement of different types of sensors and actuators. Although theillustrated embodiments of the plates are substantially flat, the platesmay take different shapes to accommodate certain types of sensors,actuators and adjoining bone or other tissue. In one embodiment, theplates may have an elastic property to allow them to slightly deformwhen a load from an adjoining bone is applied (such as that of thefemoral condyles). The elastic plates may be made from rubbers,polyurethane, silastic, gel-filled or air-filled containers.

In some embodiments, the insert may be configured with a rotatingbearing disposed in a central portion of the space between the top plateand the bottom plate. The bearing would provide for the top plate torotate relative to the bottom plate, providing an additional adjustmentthat can be made to better balance the joint. The bearing may beconfigured to provide for approximately 5-10 degrees of rotation of thetop plate with respect to the bottom plate (or vice versa depending onthe configuration of the bearing) or translation from side-to-side andfront-to-back.

The insert may also be configured with only a single plate and a set ofactuators which interface with an opposing bone surface, in oneembodiment of the invention.

Controller

FIG. 12 is an illustration of a perspective view of an embodiment of thecontroller assembly 200 of FIG. 1 connected to an insert 100. In theembodiment illustrated, the insert 100 is a pneumatic insert, such asthe insert 100 of FIGS. 4 and 5. Controller assembly 200 may include acontroller 240, a controller mount 230, and a fluid supply device 220.The controller mount 230 may be a strap or a similar mechanism formounting the controller 240 on to the patient's limb, such as the thigh.In embodiments, the controller mount 230 has a width that is the lengthof controller 240. The controller mount 230 may be affixed to thepatient's limb using a fastener, such as a hook and loop fastener. Theinsert 100 may be connected to the controller 240 by an insertconnection 55. The insert connection 55 may include the fluid supplyline 70 and the electronics connector 60 shown in FIGS. 4 to 7.

The fluid supply device 220 may be an automated source of fluid power,or may be a manually operated source of fluid power, such as a pneumaticsyringe as illustrated in FIG. 12. The fluid supply device 220 may beconfigured to supply fluid, such as a gas, to the controller 240 and tothe insert 100 to actuate the bellows 182 (shown in FIGS. 4 to 6) of theinsert 100. The gas may be air, such as room air, carbon dioxide,nitrogen, or helium. The fluid supply device 220 may be connected to thecontroller 240 by a controller supply line 225. The controller supplyline 225 may be a tube extending from the controller 240 to the fluidsupply device 220. In some embodiments, a pressure relief valve 226 maybe located at the end of controller supply line 225 adjacent controller240. The pressure relief valve 226 may ensure that the pneumaticactuator 180 is not filled above a predetermined maximum pressure, suchas 30 psi.

FIG. 13 is an illustration of a perspective view of the controller 240of the controller assembly 200 of FIG. 12. The controller 240 mayinclude a housing body 241, a housing side 243, and a housing cover 242.The housing body 241 may include the back and three sides of the housingof controller 240. Housing side 243 may attach to an end of housing body241 forming the fourth side of the housing. Housing cover 242 may fastento the housing body 241 and the housing side 243 to form the enclosureof the housing. A button membrane 244 may cover a number of buttons 251(shown in FIG. 15) that are accessible through housing cover 242. Abattery cover 249 may attach to an end of housing body 241, oppositehousing side 243 and may provide access to a battery 248 (shown in FIG.14).

FIG. 14 is an illustration of an exploded view of the controller 240 ofFIG. 13. Housing body 241 may be configured with an electronics chamber253 and an accumulator chamber 252. A battery 248 and controllerelectronics 245 may be housed within electronics chamber 253. Inembodiments, the battery 248 has enough power for the controller 240 tooperate for at least an hour. Controller electronics 245 may include,inter alia, a controller electronics board 250, buttons 251, atransmitting radio, and sensors, such as an angle sensor 254. Controllerelectronics board 250 is in electronic communication with electronicsboard 140, such as wireless or wired communication. In embodiments, theelectronics connector 60 electronically connects and is coupled to thecontroller electronics board 250 and the electronics board 140. Buttons251 may be affixed to controller electronics board 250. The angle sensor254 may provide the angle of the thigh which may indicate the angle ofthe knee flexion. The angle sensor 254 may be an accelerometer, aninclinometer, or a similar device.

The accumulation chamber 252 may smooth out pressure fluctuations as thepneumatic actuator(s) of the insert 100 undergo compression andexpansion. Housing side 243 may form a seal with housing body 241 toprevent leaking from accumulation chamber 252.

Controller 240 may also include a pressure sensor 247 for detecting thepressure of the actuating fluid within accumulation chamber 252, and asensor mount 246 configured to hold pressure sensor 247 in place. Thesensor mount 246 may be sized and shaped to be held within housing body241 by housing side 243. In embodiments the controller 240 also includesa Light emitting diode (LED). The LED may show, inter alia, when thecontroller 240 is activated.

Controller 240 may be fastened to controller mount 230 with a mountingfastener 260. In the embodiment illustrated, mounting fastener is a hookand loop fastener. In other embodiments, other types of fasteners may beused.

In some embodiments, controller functions as a wireless remote and maybe configured to transmit the data from the insert 100, including thevarious sensors and the data from the controller 240, including thepressure sensor 247, to the display system. In other embodiments,controller 240 may also serve as a display device when a suitabledisplay screen is included as part of the controller 240. In furtherembodiments, the controller 240 is directly wired to a display device.

When using the joint balancing system 50, the insert 100 may be placedwithin the appropriate joint (such as the knee joint in this example).The controller 240 may be charged by the surgeon/operator using fluidsupply device 220, such as a pneumatic syringe, to pump up the pressure.In embodiments, the pneumatic syringe is a 20 mL syringe. The pressuremay be monitored by a pressure sensor 247. The pressure may be displayedby the display module 320 in the graphic user interface on a displayscreen. In some embodiments, the optimum pressure is between 20 and 30psi. In some embodiments, the pressure may be modified to exert adefined force. The optimum force may be between 40 and 200 N. Jointbalancing system 50 may be configured to supply pressures at differentranges, depending on the application. With the insert 100 inflated (i.e.bellows expanded under pressure to actuate the insert 100), the knee isflexed (bent) through the full range of available motion. As the knee isflexed, the sensors may measure knee flexion angle, the distance betweenthe top and bottom plates of the insert, and the tilt between the topand bottom plates of the insert. This information may be graphicallydepicted by wired or wireless transmission to the display.

The surgeon can make the appropriate changes to the placement of theartificial components, to the cuts made in the bone, or to the ligamentsof the knee to generate a distraction gap and tilt that is mostdesirable for the patient.

The joint balancing system 50 may be used to balance the knee during asurgical procedure, such as a total knee arthroplasty or a partial kneearthroplasty. The controller mount 1030 may be wrapped around apatient's thigh, such as the lower thigh and tightened firmly. The hookand loop fastener of the controller mount 230 may be placed anteriorlyon the thigh. The controller 240 may be aligned with the long axis ofthe patient's thigh, with the battery cap 249 and the pressure valve 226facing proximally and the insert connection is facing distally.

The insert 100 may be positioned in between the tibial and femoralsurface. The bottom surface of the bottom plate 150 may be flat and maybe in direct or indirect contact with the tibial bone cut. The uppersurface of the top plate 110 may be curved and may be in direct orindirect contact with the femoral surface. The insert 100 should fitcomfortably and may be centered on the tibial cut surface. The surgeonmay verify that the curved upper surfaces articulate with the femoralcondyles. If the insert 100 cannot be inserted easily, the surgeon mayverify that the gap between the tibial cut surface and the femoralcondyles is at least the height of the insert 100, such as 8 mm. If theinsert 100 is too big or too small for the knee, the surgeon may selectan insert of a different size.

The actuator may then be pressurized by the fluid supply device 220 to apredetermined pressure, such as from 20 psi to 25 psi, and the displaymodule 320 may display the current pressure in the GUI. The insert 100may be expanded from a first predetermined height, such as 8 mm, wherethe insert 100 is not inflated up to a second predetermined height, suchas 14 mm, where the pneumatic actuator is fully inflated. Shims may beused when the tibiofemoral gap is greater than the second predeterminedheight. In other embodiments, the articular portion 130 may beinterchanged with a thicker articular portion 130 when the tibiofemoralgap is greater than the second predetermined height.

Once the insert 100 is positioned in the tibiofemoral gap and inflated,the joint balancing system 50 may be calibrated by holding the knee in0° flexion and selecting a calibration button displayed by the controlmodule on the GUI.

The display module 320 may also display the net gap between the tibialand femoral surfaces in real time. To check gap in flexion andextension: hold the knee in 0° and read the gap off the display. Thenflex the knee to 90° and read the gap off the display. This process canbe repeated as many times as needed. If the surgeon desires to recut thebones or reposition the components, the insert 100 can be removed (afterdeflating the controller). If the surgeon desires to perform soft-tissuereleases and there is sufficient access, he or she can perform thesoft-tissue releases with the insert in place and monitor the changinggap in real-time on the display.

Joint balancing system 50 may also be used to measure the dynamic kneebalance by flexing the knee gently between full extension and fullflexion. The display module 320 may display the net gap between thetibial and femoral surfaces in real time in the GUI as well as recordthe gap and show a plot of the tibiofemoral gap against knee flexion inthe GUI.

The balance of the knee can be changed and monitored in real time byreleasing a ligament with the insert 100 in place and monitoring thechanges in the tibiofemoral gap and tilt while the release is beingperformed. The balance of the knee can also be changed and monitored inreal time by making suitable changes to the femoral or tibial cuts torealign the components.

In some embodiments, the joint balancing system 50 may also include acorrection module. The correction module may interpret the data receivedfrom the insert 100 and the controller 240 and provide recommendationsfor a surgical procedure to correct any perceived imbalance. Thecorrection module may receive other inputs including the bone geometryfrom an imaging modality, such as preoperative CT or MRI scans, theangle between adjacent bony structures, such as the angle between thefemoral and tibial bone shafts, and ligament attachments, which may bebased on digitizing landmarks using surgical navigation instruments.

The correction module may calculate the forces across the articularsurfaces of the insert 210, such as by using rigid bodies to representthe bones and the insert 210, and using springs to represent theligaments. The correction module may refine the ligament attachments,lengths, and stiffnesses to match force displacement data collected ordetermined by the sensors in the joint balancing system 50. Thecorrection module may also calculate corrections to bone cuts and to theligaments based on the lengths, stiffnesses, current angle of bone cuts,and the angle of the tibiofemoral shaft.

If the forces are balanced mediolaterally, but tight in flexion and inextension then the correction module may calculate an amount of bone tobe cut from the proximal tibia based on the force-displacement datacollected in extension and flexion. If forces are acceptable andbalanced mediolaterally in flexion but tight in extension then thecorrection module may calculate an amount of bone to be cut from thedistal femur based on the force versus displacement data collected inextension. The correction module may provide other recommendations, suchas modifications to the ligaments based on the measured data.

Cutting Guides and Grinding Surface

FIGS. 15 and 16 illustrate an embodiment of a cutting guide assembly 400connected to the insert 100 that is used to guide cutting bone andtissue during balancing of the joint. Cutting guide assembly 400 may bemounted to the insert 100 to provide a surgeon with guides for cuttingsections of bone, cartilage or ligaments during the joint balancing.

In the embodiment illustrated, a cutting guide assembly 400 includescutting guide mounts 402, a cutting guide 406, and mounting fasteners408, such as screws or bolts. Cutting guide mounts 402 may be attachedto the insert 100 at bottom plate 150 or top plate 110.

The cutting guide 406 is attached to the cutting guide mounts 402 usingthe mounting fasteners 408. Cutting guide 406 includes one or moreguiding slots 410. In the embodiment illustrated, cutting guide 406includes two parallel guiding slots 410. The guiding slots 410 can beused to align and make cuts to the bone, cartilage, ligaments or othertissues during the process of balancing the joint and positioning theartificial joint prostheses.

The guiding slots 410 have flat surfaces that hold and guide the bladesof the cutting devices or saws while the surgeon is cutting the bones.The surgeon inserts the cutting saw into the slot of the cutting guide,which helps maintain the location and angle of the guide. In theembodiment described here, the cutting guides are mounted on the platesof the balancing insert such that the cuts are made with the ligamentsappropriately tensioned.

In some embodiment, a surface of the top plate or bottom plate may beconfigured as a grinding (or milling or planing) surface or abrasivesurface so that it operates to grind against a corresponding bonestructure and grind the bone surface into a smoother surface that willfit with the plate more readily.

Those of skill will appreciate that the various illustrative logicalblocks, modules, and algorithm steps described in connection with theembodiments disclosed herein can be implemented as electronic hardware,computer software, or combinations of both. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, and steps have been described abovegenerally in terms of their functionality. Whether such functionality isimplemented as hardware or software depends upon the design constraintsimposed on the overall system. Skilled persons can implement thedescribed functionality in varying ways for each particular application,but such implementation decisions should not be interpreted as causing adeparture from the scope of the invention. In addition, the grouping offunctions within a module, block, or step is for ease of description.Specific functions or steps can be moved from one module or blockwithout departing from the invention.

The various illustrative logical blocks and modules described inconnection with the embodiments disclosed herein can be implemented orperformed with a general purpose processor, a digital signal processor(DSP), application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor can be a microprocessor, but in thealternative, the processor can be any processor, controller,microcontroller, or state machine. A processor can also be implementedas a combination of computing devices, for example, a combination of aDSP and a microprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with theembodiments disclosed herein can be embodied directly in hardware, in asoftware module executed by a processor (e.g., of a computer), or in acombination of the two. A software module can reside in RAM memory,flash memory, ROM memory, EPROM memory, EEPROM memory, registers, harddisk, a removable disk, a CD-ROM, or any other form of storage medium.An exemplary storage medium can be coupled to the processor such thatthe processor can read information from, and write information to, thestorage medium. In the alternative, the storage medium can be integralto the processor. The processor and the storage medium can reside in anASIC.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notof limitation. The breadth and scope should not be limited by any of theabove-described exemplary embodiments. Where this document refers totechnologies that would be apparent or known to one of ordinary skill inthe art, such technologies encompass those apparent or known to theskilled artisan now or at any time in the future. In addition, thedescribed embodiments are not restricted to the illustrated examplearchitectures or configurations, but the desired features can beimplemented using a variety of alternative architectures andconfigurations. As will become apparent to one of ordinary skill in theart after reading this document, the illustrated embodiments and theirvarious alternatives can be implemented without confinement to theillustrated example. One of ordinary skill in the art would alsounderstand how alternative functional, logical or physical partitioningand configurations could be utilized to implement the desired featuresof the described embodiments. Hence, although the present disclosure,for convenience of explanation, depicts and describes an insert forbalancing a knee joint, it will be appreciated that the insert inaccordance with this disclosure can be implemented in various otherconfigurations and can be used to balance various other types of joints,such as hip, shoulder, ankle, elbow, and spine joints.

Furthermore, although items, elements or components may be described orclaimed in the singular, the plural is contemplated to be within thescope thereof unless limitation to the singular is explicitly stated.The presence of broadening words and phrases such as “one or more,” “atleast,” “but not limited to” or other like phrases in some instancesshall not be read to mean that the narrower case is intended or requiredin instances where such broadening phrases may be absent.

1.-24. (canceled)
 25. An device, comprising: a first plate configured tointerface with a first bone structure of a joint; a second plateconfigured to interface with a second bone structure of the joint,wherein the second bone structure is opposite the first bone structure;at least one actuator disposed between the first plate and the secondplate, wherein the at least one actuator is configured to apply adistraction force to the first plate and the second plate so as todistract the first bone structure from one another, and wherein theforce is configured to balance the joint while the joint is movedthrough a range of motion including at least one of flexion orextension; at least one sensor coupled to at least one of the firstplate or the second plate, wherein the at least one sensor is configuredto capture data indicative of one or more sensors configured to providedata indicative of at least one of a force or a location; and aprocessor communicatively coupled to at least one sensor, wherein theprocessor is configured (i) to receive the data from the at least onesensor, (ii) to determine data indicative of a balance of the joint, and(iii) to output the data indicative of the balance of the joint to auser.